Typically, the CD4 T cell response to complex protein antigens is limited to one or a few peptide epitopes within that antigen, despite the fact that there are many potential peptides that can bind to the MHC molecules and elicit an immune response in the host. The experiments within this application seek to understand the elements in vivo that dictate this narrowed selection of specificity in CD4 T cells. Our current data suggest that the kinetic stability of peptide:MHC class II complexes is a major element that determines whether a particular peptide:class II complex will emerge as the dominant specificity in the developing CD4 T cell response. Our experiments are designed to comprehensively examine the impact of peptide:class II stability in the selection of peptides for CD4 T cell responses. We will determine the role that kinetic stability plays in DM editing within APC, in DM-mediated peptide association and dissociation in vitro and in the priming events in vivo mediated by dendritic cells. We will use a combination of molecular, biochemical and functional approaches to definitively and critically address this issue. We will evaluate peptides from independent and unrelated source antigens to determine degree of linkage between kinetic stability of peptide:MHC complexes, DM editing and immunodominance. Additionally, in order to extend our studies beyond correlative relationships, a major approach that will be used in the proposed experiments is to design peptide variants of selectively modulated kinetic stability that can be used in antigen presentation studies, biochemistry experiments and in immunization studies. The experiments within this application thus seek to demonstrate a causative relationship between the kinetic stability of peptide class II complexes with their immunological fate in the developing immune response. |